Currently, test stands are used to perform endurance tests on high power alternating current (AC) generators, such as aircraft generators. A typical test stand comprises a prime mover, a gearbox installed between the prime mover and a generator under test, a resistive load bank, a generator control unit (GCU) with associated potential and current sensors at the point-of-regulation (POR), generator cooling accessories and support instrumentation. The prime mover is commonly a direct current (DC) motor, although an AC motor with a suitable motor controller is also satisfactory.
A resistive load bank typically comprises a set of water-cooled resistive elements that are switched by a corresponding set of mechanical relays. The resistive load bank operates inherently at the unity power factor (PF) and has a very fast loading response due to characteristics of mechanical contactors of the relays. When variable leading (capacitive) or lagging (inductive) load is required, an additional resistive-inductive-capacitive (RLC) load bank is connected to the POR. Loading the generator with a resistive load bank is required to characterize generator electrical performance, such as load-on and load-off transient responses. However, for generator endurance testing at rated power, the resistive load bank is very inefficient since electrical energy is wasted in the resistive elements.